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factor of acidity is expressed in terms of pH value. In general it may be said that fruits, tomatoes, kraut and rhubarb have a pH value below 4.5 and that therefore those products when packed under proper sanitary conditions are not subject to botulinus spoilage.

The subject of the pH value of foods and the meaning of the terms are given in National Canners' Association Bulletin 17-L. That bulletin also includes on page 6 a chart showing the pH value of a considerable number of canned foods. It is sufficient here to say that water, which is neutral, has a pH value of 7. Nearly all foods are more or less acid. The more acid a food the lower its pH value. The more alkaline it is the higher the pH value.

In classing fruits as products with a pH value below 4.5 is meant to include only those fruits which are not subjected to chemical treatment in preparation for canning. Ripe olives are soaked in weak lye in the curing operation, and this lye changes their pH value so that the product requires a much heavier process to insure its sterilization than is necessary with other fruits.

On the other hand, in the lye peeling of peaches and tomatoes the treatment with lye is brief and the excess is immediately washed away. Even if the lye should not be all removed in washing the remainder would go into combination with the acid. The lye peeling of fruits does not appreciably change their pH value.

Nearly all products with a higher pH value than 4.5 should be processed so that all portions of the can will be heated sufficiently to destroy the most resistant strains of B. botulinus.

The time and temperature of processing necessary with each canned product under the usual canning conditions is being determined by the Research Laboratory of the National Canners' Association. These processes are based on the results of the botulism studies mentioned above and the heat penetration of the various products, determined under commercial canning conditions. Sufficient data are now at hand to enable the Research Laboratory during the coming winter to formulate safe processes for all products with a pH value above 4.5 that are commonly packed. Processes have already been published by the laboratory for corn, peas and string beans.


A system should be adopted in every plant that will make it possible to identify each can with the batch with which it was processed, with the block in the warehouse in which it was stored, or with a lot of cans no larger than a day's run on a single line. There are many reasons why such a system of coding should be adopted. Among these reasons are the following:

IDENTIFIES POOR RAW PRODUCTS.—It sometimes happens that some imperfection in the raw product, indiscernible until after canning, results in an abnormal appearance, odor or taste in the finished product. REVEALS MISTAKES IN BRINING. A mistake is sometimes made in the strength of brine or syrup.

SEPARATES DEFECTIVE CANS.-Imperfections in the can and improper double-seaming are usually limited to relatively small lots.

FAVORS ACCURATE GRADING.-Because of some peculiarity of the raw product it is discolored by the process more at some times than others. In such cases coding sometimes makes it possible to grade the canned

2 See footnote, page 461.

product according to color or to separate out a quantity of goods whose colors is not up to the average.

CORRECTS IMPROPER FILLING.-A mistake in the operation of the filler or miscalculation of the extent to which goods will swell or shrink sometimes causes the improper filling of canned foods which is only detected after the goods are stored.

CORRECTS ERRORS IN PROCESSING.-A mistake in either time or temperature of processing may result in a single batch of cans being. under-processed or overcooked. On incubating samples as suggested below it may be found that the process employed is insufficient. In such cases it is of the utmost importance to be able to separate all goods shown to be underprocessed.

In all these cases and perhaps in others it is a distinct advantage to the canner to be able to separate a certain lot of his goods and sell them according to sample or exclude them from sale, or perhaps reprocess them before spoilage begins.

Many canners have adopted some system of coding. The milk condensers as a rule number each batch separately, and the same practice has been found advantageous by canners of tomato pulp. Fruit and vegetable canners often mark their cans so as to designate the number of the line and the day in which the product was put up.

The importance of coding is emphasized in this connection because when understerilization occurs, coding permits a canner to separate all cans that have received a questionable process and handle them as suggested below.


It is believed that the recommendations given above if followed without variation will yield a product entirely safe with respect to botulism (and indeed with respect to all kinds of illness that could be caused by bacterial contamination). We must not lose sight of the fact, however, that a slip in any operation is always possible. The uncertainty of the human factor must always be considered and guarded against. With this in view it is strongly recommended that cans be withdrawn systematically from all products having a pH value greater than 4.5 (that is, from all products other than tomatoes, kraut, rhubarb and the ordinary fruits) and incubated for at least five days at a temperature not less than 90° F. and not higher than 100° F.

ASCERTAIN CAUSE OF SPOILAGE.-If such incubation shows material spoilage, every effort should be made to ascertain the cause of the spoilage. Unless it is found to be due to some other cause than underprocessing, the swelled cans should be destroyed and the flat cans resterilized by safe processing procedures.

RELATION OF SPOILAGE TO BOTULISM.-In this connection it should be emphasized that excessive spoilage, due to understerilization, of products having a greater pH value than 4.5, indicates the possibility

'Molasses and syrup should not be incubated. Continued heating of such products liberates a gas which bulges the ends of the can though the product is sterile. Moreover, B. botulinus will not grow in products of this class. It is questionable also whether incubation is practicable with fruits in very heavy syrups.

of living B. botulinus spores. The Bureau of Chemistry has suggested that the reprocessing of such foods is necessary to safeguard against botulism. When a batch has shown such understerilization it is possible that even cans that show no evidence of spoilage may cause sickness or death. It has been definitely shown that packs of underprocessed spinach, for example, which contained B. botulinus also exhibited a high percentage of general spoilage.

SPRINGERS NOT Proof of SpoilaGE. In examining goods that have been incubated it must be borne in mind that cans which do not have a very high vacuum will spring when heated to the termperature of the incubator. Cans should not be condemned, therefore, because of being springers or even fairly hard swells while in the incubator. Such cans should not be judged until they have been removed from the incubator and cooled to room temperature.

GENERAL VALUE OF INCUBATION.-Incubation is suggested above especially for products which may possibly be subject to botulinus spoilage. In this connection, however, it is desired to emphasize the fact that the value of incubation is not by any means limited to safeguarding against botulism. The practice is well worth while as a general precaution in canning foods of nearly all varieties. It is only in this way that some of the errors pointed out above under Coding can be detected in time to save loss from spoilage.

Electrical appliances are now so well perfected that it is a simple matter to control the temperature of an incubation room within the desired range. The walls of the room should be insulated to prevent loss of heat and the room should be so arranged and the samples so placed as to permit good distribution of air in order that the temperature of the various portions of the room will be uniform.


It will be noted that reprocessing is not recommended even in the case of excessive spoilage when it is definitely shown that such spoilage is due entirely to some other cause than underprocessing. For instance, heavy spoilage may be due to the causes mentioned below.

KINDS OF SPOILAGE NOT RELATED TO B. BOTULINUS.-Improperly made cans or cans improperly double-seamed; improper cooling of cans, thus permitting the development of thermophilic bacteria, which are far more resistant than B. botulinus and which cannot be entirely destroyed in processing certain foods; stack-burning, which occurs when tomatoes and certain fruits are enclosed in tight cases or stacked in the warehouse without sufficient cooling.

SPRINGERS NOT PROOF OF SPOILAGE.-It must also be kept in mind that the bulging of cans is not necessarily proof of spoilage. For instance, when some products, especially fruits, are not properly cooled before they are stacked or when they are stored in a hot warehouse and especially for a long time the hydrogen gas formed by the action of the fruit acids on the can causes the bulging of the ends, which is mistaken by many for spoilage.

When cans are overfilled with certain products and when they are

filled at too low a temperature and sometimes when they are improperly cooled before stacking (especially under certain conditions of filling and double-seaming), springers result, which are mistaken by some as evidence of spoilage. Springers are not merchantable and should not be sold to consumers, but should not be classed with swells caused by bacterial decomposition.

RESPONSIBILITY OF DISTRIBUTOR.-After canned foods are shipped it is not within the power of the canner to control the conditions under which they are stored. When canned foods deteriorate after shipment because of improper storage the responsibility rests with the distributor and not with the canner. Such deterioration is not a factor in the production of botulism but is intimately connected with the merchantability of the goods. The distributor, therefore, has a grave responsibility in connection with the spoilage of foods.

PROCEDURE WITH UNDERPROCESSED FOODS.-If in products with a pH value above 4.5 the spoilage due to underprocessing is found to be material, the swelled cans should be destroyed and the cans which appear normal should be reprocessed as directed under Incubation. Before such action is taken, however, the cause of the spoilage should be accurately determined. Reprocessing of the normal cans is obviously of no value if the spoilage is due to any other cause than understerilization.

DIRECTIONS FOR REPROCESSING.-When reprocessing is found necessary the cook should be at the same temperature and for a longer time (depending on the nature of the product) than is required for processing raw products. The bacteria present require as severe heat treatment as if no processing had occurred and the cans being cold will require a longer time for the heat to penetrate than in the original process.

To Growers

Circular on Pruning

Issued by the Canners' League of California, 1922.

With the approach of the pruning season, we wish to urge upon the grower the necessity of giving to the pruning operation the serious consideration it merits.

Keep in mind the very important fact that an extra few minutes spent on each tree at pruning time may save hours per tree at thinning time, and, which is equally important, leave the tree in condition to put forth the proper amount of well placed, vigorous fruit wood for the year following.

Prune thoroughly. Don't leave too much bearing wood, thus wasting the vitality of the tree producing pits.

Regularity of bearing is very much to be desired. Under-pruning and under-thinning are the two greatest known enemies of regularity of production. Over a period of years the orchard that has not been overcropped will show the largest average tonnage of first-class fruit.

Regardless of the style of pruning a grower may adopt, fruit wood should be thinned out to a point where it is certain the tree can safely

carry the load, for broken down trees are neither a source of pride nor profit.

A broken main limb on a mature tree bares the heart of the tree to deadly wood decay.

A tree that has been weakened by over-cropping or lack of care is more susceptible to frost, disease or adversity of any sort than a tree that has been conservatively cropped and well cared for.

There can be no doubt that young trees require far less pruning than has been the general practice; therefore, so-called long pruning may be recommended as the method best adapted to the requirements of non-bearing trees.

The application of the long-pruning principle to bearing peach trees has not yet been successfully demonstrated.

Long pruning doesn't mean less pruning.

Long pruning is not necessarily an easier way of pruning.

Long pruning is not a cheaper way of pruning.

Long pruning of bearing peach trees has not yet stood the test of time in commercial orchard practice.

The old standard pruning method on bearing trees has been evolved from the combined judgment and experience of years of successful production of the highest quality fruit.

We most earnestly recommend that bearing peach trees be pruned by this standard method. You can't go wrong at this time if you follow it. Let's not move the California Peach Industry off Quality Street.

Treatment of Tomato Seed to Prevent Bacterial Spot Circular issued by National Canners' Association, January 28, 1921. A disease of tomatoes attacking both fruits and plants has recently been described by the Indiana Experiment Station. The trouble is apparently rather common in the Middle West, and a fairly wide distribution in the East is suspected.

The disease causes small irregular black or brown scab-like spots which develop on the tomatoes. These are broken up in the cyclone, and may be the cause of black specks in the finished product as well as the cause for reduced yields in the field.

Dr. Max W. Gardner, of the Indiana Station, has found that the disease is disseminated principally on the seed, and that it may be controlled by seed treatment with a solution of corrosive sublimate. In a statement released by the Director of the Indiana Station a few days ago the following directions are given for the treatment of the seed:

"Place the dry seed in a rather large cheese cloth bag and immerse it in a 1 to 3,000 solution of corrosive sublimate for five minutes. Stir thoroughly by poking the bag with a stick so as to remove air bubbles and insure thorough wetting of the seed coats.

"Remove the bag of seed from the corrosive sublimate solution after five minutes' immersion and wash for ten to fifteen minutes in running water. After this, the excess water should be gently pressed from the bag and the seed spread out in a thin layer in a well ventilated place to dry.

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